Abstract:

A projecting zoom lens includes in order from a magnification side, a
first negative group, second, third and fourth positive groups, a fifth
negative group and a sixth positive group. The third group, the fourth
group and the fifth group are moved along the optical axis to the
magnification side during zooming from the wide-angle end to the
telephoto end, and such that the projecting zoom lens satisfies given
following conditional expressions.
0.9<|f1|/fw<1.7 (1)
55<νd4 (2)

Claims:

1. A projecting zoom lens comprising, in order from a magnification side:a
first lens group having a negative refractive power;a second lens group
having a positive refractive power;a third lens group having a positive
refractive power;a fourth lens group having a positive refractive power;a
fifth lens group having a positive or negative refractive power; anda
sixth lens group having a positive refractive power;wherein the third to
fifth lens groups are moved along an optical axis toward the
magnification side during zooming from a wide-angle end state to a
telephoto end state andthe following Conditional Expressions (1) to (2)
are satisfied:0.9<|f1|/fw<1.7 (1)55<νd4 (2)where f1
denotes a focal length of the first lens group,fw denotes a focal length
of the projecting zoom lens at the wide angle end state, andνd4
denotes an Abbe number of glass material of which a positive lens
contained in the fourth lens group is made.

2. A projecting zoom lens according to claim 1,wherein the first lens
group and the sixth lens group are fixed during zooming.

3. A projecting zoom lens according to claim ifwherein the first lens
group is moved along the optical axis during focusing.

4. A projecting zoom lens according to claim 1,wherein the second lens
group includes a positive lens having a convex face directed toward a
reduction side, andthe third lens group includes a positive lens having a
convex face directed toward a magnification side.

5. A projecting zoom lens according to claim 1,wherein the following
Conditional Expression (3) is satisfied:1.7<Nav (3)where Nav denotes
mean value of refractive indices at d-line of (i) glass material of which
a positive lens contained in the second lens group is made and (ii) glass
material of which a positive lens contained of third lens group is made.

Description:

[0001]This application is based on and claims priority under 35 USC 119
from Japanese Patent Application No. 2007-165191 filed Jun. 22, 2007.

BACKGROUND

[0002]1. Technical Field

[0003]The present invention relates to a projecting zoom lens having six
groups and mounted on a projection type display device or the like and to
a projection type display device having the projecting zoom lens mounted
thereon and, more particularly, to a projecting zoom lens and a
projection type display device for magnifying and projecting such a
luminous flux on a screen carrying video information from a light valve
of a liquid crystal display device or a DMD (Digital Micromirror Device)
display device.

[0004]2. Related Art

[0005]In recent years, there becomes widespread the projection type
display device using the light valve such as the liquid crystal display
device or the DMD display device. This widely used device is constituted
such that three light valves are used to correspond respectively to the
illuminating lights of the three primaries RGB thereby to modulate those
illuminating lights, and such that the lights modulated by the respective
light valves are synthesized by a prism or the like and are displayed
through a projection lens on a screen.

[0006]In the light valves described above, the size reduction and the high
precision advance abruptly, and the personal computers become widespread.
As a result, the demands for presentations using that projection type
display device are rising. Thus, the projection type display device is
demanded to have a higher performance, a smaller size and a lighter
weight.

[0007]In the projection type display device, in which the respective
modulated lights from the three light valves are synthesized and
projected by a color synthesizing optical system, the projecting lenses
requires long back focuses to arrange prisms for the color
synthesization. In the color synthesizing optical system, moreover, the
spectroscopic characteristics are changed by the angles of incident
lights, so that the projecting lenses requires the characteristics, in
which the incident pupils seen from the reduction side are sufficiently
distant, that is, the telecentricity. There are further needed bright
lenses and aberration corrections matching the resolution of the device.
In the case of the front type, the zooming function and the wide-angle of
view are also demanded from the viewpoint of mountability. In accordance
with the size reduction of the light valve itself, the increased demand
for the mobile application and the reduced price of the projector,
moreover, there is a tendency to demand the smaller size and lighter
weight form the projection lens.

[0008]As the projection lens capable of satisfying those demands, there
are known a number of zooming types (as referred to Patent Documents 1
(JP-A-2004-138812)and 2 (JP-2006-162734), for example), in which the
lenses are composed of, in order from the magnification side, five groups
of negative--positive--positive--positive (or negative)--positive such
that the second, third and fourth lens groups are moved during zooming
along the optical axis, and the first lens group and the fifth lens group
are fixed.

[0009]In the following Patent Documents 3 (JP-A-2006-184723) and 4
(JP-A-2006-317976), for example, there are another zooming type, in which
the lenses are composed of, in order from the magnification side, six
groups of negative--positive--positive--positive--positive (or
negative)--positive and the first lens group and the sixth lens group are
fixed.

[0010]It is known that the performance of a lens may be improved if the
degree of freedom for optical designs may be raised by increasing the
number of lens or the zoom moving groups. However, the increase in the
number of lens portions leads directly to the upsizing of the device or
the rise of the cost, and the spectral transmittance is lowered if the
thickness of the glass material of the entire lens system increases. The
drop of the spectral transmittance is serious especially on the shorter
wave side, and is disadvantageous especially in the projecting optical
system, for which it is difficult to adjust directly the projected image
having passed through the projection lens.

[0011]The present invention has been conceived in view of the background
thus far described, and has an object to provide an inexpensive
projecting zoom lens, which can hold the telecentricity on a reduction
side while achieving a wide-angle of view, which can correct
satisfactorily various aberrations such as spherical aberrations,
longitudinal chromatic aberrations and field curvatures, and which can
achieve the size reduction even with high brightness and performance, and
a projection type display device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 shows a schematic view showing a constitution of a projecting
zoom lens according to Embodiment 1 of the invention.

[0013]FIG. 2 shows a schematic view showing a constitution of a projecting
zoom lens according to Embodiment 2 of the invention.

[0014]FIG. 3 shows a schematic view showing a constitution of a projecting
zoom lens according to Embodiment 3 of the invention.

[0015]FIG. 4 shows a schematic view showing a constitution of a projecting
zoom lens according to Embodiment 4 of the invention.

[0016]FIG. 5 shows a schematic view showing a constitution of a projecting
zoom lens according to Embodiment 5 of the invention.

[0017]FIG. 6 shows a schematic view showing a constitution of a projecting
zoom lens according to Embodiment 6 of the invention.

[0024]FIG. 13 shows a schematic constitution diagram of a projection type
display device according to one mode of embodiment of the invention.

SUMMARY

[0025]According to an aspect of the invention, a projecting zoom lens
includes in order from magnification side, a first lens group having a
negative refractive power, a second lens group having a positive
refractive power, a third lens group having a positive refractive power,
a fourth lens group having a positive refractive power, a fifth lens
group having a positive or negative refractive power and a sixth lens
group having a positive refractive power. The third to fifth lens groups
are moved along an optical axis toward the magnification side during
zooming from a wide-angle end state to a telephoto end state. And
following Conditional Expressions (1) to (2) are satisfied:

0.9<|f1|/fw<1.7 (1)

55<νd4 (2)

where f1 denotes a focal length of the first lens group, fw denotes a
focal length of the projecting zoom lens at the wide angle end state and
νd4 denotes an Abbe number of glass material of which a positive lens
contained in the fourth lens group is made.

[0026][2] According to the projecting zoom lens of [1], the first lens
group and the sixth lens group may be fixed during zooming.

[0027][3] According to the projecting zoom lens of [1] or [2], the first
lens group may be moved along the optical axis during focusing.

[0028][4] According to the projecting zoom lens of [1], [2] or [3], the
second lens group may include a positive lens having a convex face
directed toward a reduction side. The third lens group may include a
positive lens having a convex face directed toward a magnification side.

[0029][5] According to the projecting zoom lens of [1], [2], [3] or [4],
the following Conditional Expression (3) may satisfied:

1.7<Nav (3)

[0030]where Nav denotes mean value of refractive indices at d-line of (i)
glass material of which a positive lens contained in the second lens
group is made and (ii) glass material of which a positive lens contained
of third lens group is made.

[0031]According to a projecting zoom lens of [1], [2], [3], [4] or [5], a
projection type display device includes a light source, a light valve, an
illuminating optical unit that guides the luminous flux from the light
source to the light valve, a projecting zoom lens of [1], [2], [3], [4]
or [5]. The light valve modulates the luminous flux from the light
source. The projection type display device projects the modulated
luminous flux on a screen.

[0032]According to the projecting zoom lens of the invention, the
projecting zoom lens includes six groups, among which the power, the
zooming function and the aberration correcting function are properly
distributed, so that zooming ratio of about 1.2, F number of 1.6 in the
wide-angle end state are achieved while balancing the aberrations,
thereby to provide an inexpensive wide-angle zoom lens which is small in
size and excellent in mass production.

[0033]Moreover, the conditional expression (1) is defined to set the power
distribution to the first lens group properly in the wide-angle end
state. If the ratio is lower than the lower limit of the conditional
expression (1), the power of the first lens group is excessively strong
and thereby make it difficult to correct the aberrations produced by each
lens group. If the ratio is higher than the upper limit, on the other
hand, the power of the first lens group becomes so relatively low that
the enlargement of the optical system is invited if the focal length of
the entire system is kept within a given range.

[0034]By satisfying the conditional expression (1), therefore, the optical
system may be made compact while making the correction of the aberration
satisfactory.

[0035]Next, the conditional expression (2) is defined to correct a
longitudinal chromatic aberration. If the Abbe number falls short of the
lower limit of the conditional expression (2), the longitudinal chromatic
aberration increases to cause bleeding.

[0036]By satisfying the conditional expression (2), therefore, the
longitudinal chromatic aberration may be reduced to suppress the
bleeding.

[0037]Moreover, the conditional expression (3) is one for correcting the
image curvature, If the refractive index falls short of the lower limit
of the conditional expression (3), the Petzval sum increases to become a
factor to deteriorate the focusing in a region apart from the optical
axis.

[0039]Specific modes of embodiments of the invention are described in the
following with reference to the accompanying drawings. A projecting zoom
lens of a mode of embodiment (showing the wide-angle end state of
Embodiment 1 representatively) , as shown in FIG. 1, includes in order
from a magnification side, a first lens group G1 having a negative
refractive power, second to fourth lens groups G2 to G4 respectively
having positive refractive powers, a fifth lens group G5 having a
negative refractive power and a sixth lens group G6 having a positive
refractive power. In rear of the projecting zoom lens, there are arranged
a glass block (containing a filter portion) 2 constituted mainly of a
color synthesizing prism, and an image display face 1 of a light valve
such as a liquid crystal display panel. Incidentally, letter X denotes an
optical axis.

[0040]Here, the first lens group G1 includes, in order from the
magnification side, a first lens L1 made of a positive lens, a second
lens L2 made of a negative meniscus lens having a convex face directed to
the magnification side, and a third lens L3 made of a biconcave lens. The
second lens group G2 includes a fourth lens L4 made of a positive lens
having a convex face directed to the reduction side. The third lens group
G3 includes a fifth lens L5 made of a positive lens having a convex face
directed to the reduction side. The fourth lens group G4 includes a sixth
lens L6 made of a biconcave lens and a seventh lens L7 made of a biconvex
lens. The fifth lens group G5 includes in order from the magnification
side, an eighth lens L8 made of a lens of a low power having a convex
face directed to the magnification side, a cemented lens by cementing a
ninth lens L9 made of a biconcave lens and a tenth lens L10 made of a
biconvex lens, and an eleventh lens L11 made of a positive lens. The
sixth lens group G6 includes a twelfth lens L12 made of a positive lens.

[0041]Here, the lens constitutions of the aforementioned respective lens
groups should not be limited to the aforementioned ones, but may be
modified by increasing or decreasing one or more negative lens or
positive lens.

[0042]Moreover, the fifth lens group G5 may also be constituted to have a
positive refractive power.

[0043]The projecting zoom lens of the present mode of embodiment is a
negative lead type zoom lens, as has been described hereinbefore, so that
it is possible to make a wide-angle and to retain the back focus with a
proper length.

[0044]Moreover, the projecting zoom lens of this mode of embodiment is
constituted to have a zooming function by moving the three lens groups of
third lens group G3 to the fifth lens group G5. Specifically, the whole
lens system is divided into six groups and the zooming function is
divided for the respective groups so that the three lens groups
independently moves during zooming. As a result, it is possible to
improve the optical performance and to suppress the fluctuation of an F
number accompanying the magnification.

[0045]Moreover, it is preferred that all the three lens groups of the
third lens group G3 to the fifth lens group G5 are moved to the
magnification side during zooming from the wide-angle end to the
telephoto end. In this mode of embodiment thus constituted, it is
possible to set the zooming ratio higher.

[0046]However, this means that the positions in the telephoto end state
are set closer to the magnification side than the positions in the
wide-angle end state, but does not exclude the once movement to the
reduction side in an intermediate region.

[0047]Here, the second lens group G2 is fixed not only during zooming but
also focusing so that it makes no contribution to that action. In case
the aforementioned zoom lenses of the constitution of five groups and the
three moving groups, as described in the aforementioned Patent Documents
1 and 2, it is conceivable that the second lens group G2 is optimized by
coupling it to the third lens group G3 positioned in rear of the second
lens group G2. In this case, in the wide-angle end state, the lenses
contained in the second lens group G2 are moved in association with the
third lens group C3 more to the reduction side than the zoom lens
according to the invention.

[0048]Generally, the principal ray of an off-axis luminous flux is close
to the optical axis if the principal ray is close to a diaphragm. As
compared with a parallel plane plate, on the other hand, the inclination
of the incident light on a spherical lens with respect to a plane normal
to the optical axis becomes the larger as it leaves the optical axis the
more. In the zoom lens according to the invention, the off-axis luminous
flux is subjected to a stronger refraction in the second lens group G2
positioned closer to the magnification side than the case, in which the
second lens group G2 and the third lens group G3 are cemented. As a
result, the enlargement of the effective diameter of the rear portion of
the focus group may be suppressed to provide an advantage on the aspect
of the weight reduction of the projecting zoom lens.

[0049]The zoom lens composed of six groups and four moving groups, in
which the second lens group G2 is movable independently of the remaining
lens groups, as disclosed in Patent Documents 3 and 4, is advantageous in
the aberration correction, because the degree of freedom for optical
designs increases. However, this constitution invites an increase in the
number of mechanical parts or the size of a cam cylinder, so that it is
not desired from the view points of a lower cost and a lighter weight.

[0050]Moreover, the projecting zoom lens of this mode of embodiment is
constituted to satisfy the following Conditional Expressions:

0.9<|f1|/fw<1.7 (1)

55<νd4 (2)

and

1.7<Nav (3)

where

[0051]f1 denotes the focal length of the first lens group G1, fw denotes
the focal length of the entire lens system in the wide-angle end state,
νd4 denotes the Abbe number of glass material of which the positive
lens contained in the fourth lens group G4 is made and Nav denotes mean
value of the refractive indices at d-line of glass material of which the
positive lens in the second lens group G2 and glass material of which the
positive lens contained in the third lens group 63 is made.

[0052]Here are described the technical meanings of the aforementioned
conditional expressions (1) to (3).

[0053]At first, the conditional expression (1) is defined to make the
optical system compact while making the aberration correction
satisfactory. Specifically, if the ratio is lower than the lower limit of
the conditional expression (1), the power of the first lens group is
excessively strong and thereby make it difficult to correct the
aberrations produced by each lens group. If the ratio is higher than the
upper limit, on the other hand, the power of the first lens group becomes
so relatively low that the enlargement of the optical system is invited
if the focal length of the whole system is kept within a predetermined
range.

[0054]From this gist, it is more preferred that the following conditional
expression (1') is satisfied in place of the Conditional Expression (1):

1.0<|f1|/fw<1.6 (1')

[0055]Next, the conditional expression (2) is defined to reduce a
longitudinal chromatic aberration thereby to suppress the occurrence of
bleeding. If the Abbe number falls short of the lower limit of the
conditional expression (2), more specifically, the longitudinal chromatic
aberration increases to cause the bleeding.

[0056]Moreover, the conditional expression (3) is defined to correct the
image curvature excellently. If the mean value falls short of the lower
limit of the conditional expression (3), the Petzval sum increases to
become a factor to deteriorate the focusing in a region apart from the
optical axis.

[0057]Here, some (Examples 4 to 6) of the following Examples contain an
aspheric lens, the aspheric shape of which is expressed by the following
aspheric equation:

[A spheric Equation]

Z = Y 2 / R 1 + 1 - K × Y 2 / R 2 + i = 3
16 A i Y i

[0058]where Z denotes the length of a normal to a tangent plane (or a
plane normal to the optical axis), from a point on an aspheric plane of a
distance Y from the optical axis, Y denotes the distance from the optical
axis, R denotes the radius of curvature of the aspheric plane near the
optical axis, K denotes an eccentricity and A1 denotes an aspheric
coefficient (i=3 to 16).

[0059]Next, one example of the projection type display device having the
aforementioned projecting zoom lens mounted thereon is described with
reference to FIG. 13. The projection type display device, as shown in
FIG. 13, is provided with transmission type liquid crystal panels 11a to
11c as light valves, and employs a projecting zoom lens 10 according to
the aforementioned mode of embodiment. Between a light source 20 and, a
dichroic mirror 12, on the other hand, there is arranged an integrator
(although not shown) such as a fly-eye. The white light from the light
source 20 is incident through an illuminating optical unit on the liquid
crystal panels 11a to 11c corresponding to three color optical fluxes (or
a G-light, a B-light and an R-light), so that it is optically modulated,
and is color-synthesized by a cross dichroic prism 14 so that it is
projected on the not-shown screen by the projecting zoom lens 10. This
device is provided with the dichroic mirrors 12 and 13 for the color
separations, the dichroic prism 14 for the color synthesization,
condenser lenses 16a to 16c, and total reflection mirrors 18a to 18c. The
projection type display device of this mode of embodiment employs the
projecting zoom lens according to this mode of embodiment so that it can
be excellent in the wide-angle and in the projected image quality and can
be bright and compact.

[0060]Here, the projecting zoom lens of the invention should not be
limited in this using mode to the projecting zoom lens of the projection
type display device employing the transmission type liquid crystal
display panel, but could also be used as the projecting zoom lens of a
device employing another optical modulation unit such as a reflection
type liquid crystal display panel and a DMD.

[0061]The projecting zoom lens of the invention is further described in
the following in connection with its specific embodiments.

Embodiment 1

[0062]The projecting zoom lens according to this Embodiment 1 is made to
have the constitution of FIG. 1, as has been described hereinbefore. In
this projecting zoom lens, specifically, the first lens group G1 includes
in order from the magnification side, a first lens L1 made of a biconvex
lens, a second lens L2 made of a negative meniscus lens having a convex
face directed to the magnification side and a third lens L3 made of a
biconcave lens The second lens group G2 includes a fourth lens L4 made of
a positive meniscus lens having a convex face directed to the reduction
side. The third lens group G3 includes a fifth lens L5 made of a biconvex
lens. The fourth lens group G4 includes in order from the magnification
side, a sixth lens L6 made of a biconcave lens and a seventh lens L7 made
of a biconvex lens. The fifth lens group G5 includes in order from the
magnification side, an eighth lens L8 made of a lens of a low power
having a convex face directed to the magnification side, a cemented lens
by cementing a ninth lens L9 made of a biconcave lens and a tenth lens
L10 made of a biconvex lens, and an eleventh lens L11 made of a biconvex
lens. The sixth lens group G6 includes a twelfth lens L12 made of a
biconvex lens.

[0063]Here in this embodiment, the fifth lens group C5 is constituted to
have a negative refractive power.

[0064]In this Embodiment 1, the radius of curvature R (as standardized for
the focal length of 1 mm of the whole lens system, as in the following
individual tables) of each lens surface; the center thickness of the
respective lenses and the air distance D (as standardized like the
aforementioned radius of curvature R, as in the following individual
tables) between the respective lenses; and the refractive indices Nd and
the Abbe numbers νd at the d-line of the respective lenses are
tabulated in Table 1. Here, in this Table 1 and in the subsequent Tables
2 to 6, the numerals corresponding to the respective symbols R. D, Nd and
νd are increased sequentially from the magnification side.

[0065]The mask is not shown in FIG. 1 but may be arranged, and may be
exemplified by an aperture diaphragm.

[0067]FIG. 7 presents aberration diagrams showing several aberrations
(i.e., spherical aberrations, astigmatisms, distortions, and lateral
chromatic aberrations) of the projecting zoom lens of Embodiment 1. Here
in FIG. 7 and subsequent FIG. 8 to FIG. 12: the respective spherical
aberrations show the aberrations for lights having the wavelengths of
460.0 nm, 546.07 nm and 615.0 nm; the respective astigmatisms show the
aberrations for a sagittal image surface and a tangential image surface;
and the respective lateral chromatic aberrations show the aberrations of
460.0 nm and 615.0 nm for the light having the wavelength of 546.07 nm.

[0068]According to the projecting zoom lens of Embodiment 1, as apparent
from FIG. 7, the angle of view 2ω is as wide as 57.4 degrees, and
the respective aberrations are satisfactorily corrected.

[0069]As tabulated in Table 7, moreover, the conditional expressions (1),
(1'), (2) and (3) are satisfied according to the projecting zoom lens of
Embodiment 1.

Embodiment 2

[0070]The schematic constitution of the projecting zoom lens according to
Embodiment 2 is shown in FIG. 2. The projecting zoom lens according to
Embodiment 2 is given a constitution substantially similar to that of
Embodiment 1, and the fifth lens group G5 is also constituted to have a
negative refractive power.

[0071]In this Embodiment 2, the radius of curvature R of each lens
surface, the center thickness of the respective lenses and the air
distance D between the respective lenses, and the refractive indices Nd
and the Abbe numbers νd at the d-line of the individual lenses are
tabulated in Table 2.

[0074]According to the projecting zoom lens of Embodiment 2, as apparent
from FIG. 8, the angle of view 2ω is as wide as 57.4 degrees, and
the respective aberrations are satisfactorily corrected.

[0075]As tabulated in Table 7, moreover, the conditional expressions (1),
(1'), (2) and (3) are satisfied according to the projecting zoom lens of
Embodiment 2.

Embodiment 3

[0076]The schematic constitution of the projecting zoom lens according to
Embodiment 3 is shown in FIG. 3. The projecting zoom lens according to
Embodiment 3 is given a constitution substantially similar to that of
Embodiment 1, and the fifth lens group G5 is also constituted to have a
negative refractive power. From Embodiment 1, however, Embodiment 3 is
different in that the fourth lens group G4 consists of the sixth lens L6
made of a positive lens.

[0077]Here, the projecting zoom lens of Embodiment 3 is different in the
number of lenses from Embodiment 1, so that the given lens numbers are
sequentially shifted according to the differences.

[0078]In this Embodiment 3, the radius of curvature R of each lens face,
the center thickness of the respective lenses and the air distance D
between the respective lenses, and the refractive indices Nd and the Abbe
numbers νd at the d-line of the respective lenses are tabulated in
Table 3.

[0081]According to the projecting zoom lens of Embodiment 3, as apparent
from FIG. 9, the angle of view 2ω is as wide as 57.2 degrees, and
the respective aberrations are satisfactorily corrected.

[0082]As tabulated in Table 7, moreover, the conditional expressions (1),
(1'), (2) and (3) are satisfied according to the projecting zoom lens of
Embodiment 3.

Embodiment 4

[0083]The schematic constitution of the projecting zoom lens according to
Embodiment 4 is shown in FIG. 4. The projecting zoom lens according to
Embodiment 4 is given a constitution substantially similar to that of
Embodiment 1, but is different mainly in that the third lens L3 made of a
thin resin lens added for forming an aspheric surface to the reduction
side of the second lens L2 in the first lens group G1, in that the fourth
lens group G4 consists of the sixth lens L6 made of a positive lens, and
in that the fifth lens group G5 is constituted to have a positive
refractive power.

[0084]Here, the projecting zoom lens of Embodiment 4 is different in the
number of lenses from Embodiment 1, so that the given lens numbers are
sequentially shifted according to the differences.

[0085]In this Embodiment 4, the radius of curvature R of each lens face,
the center thickness of the respective lenses and the air distance D
between the respective lenses, and the refractive indices Nd and the Abbe
numbers vd at the d-line of the respective lenses are tabulated in Table
4.

[0086]Moreover, the fifth surface (or the surface of the reduction side of
the third lens L3) is made a spheric, and the respective values K, A3,
A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15 and A16 are
tabulated for those individual aspheric planes in the lower column of
Table 4.

[0089]According to the projecting zoom lens of Embodiment 4, as apparent
from FIG. 10, the angle of view 2ω is as wide as 57.4 degrees, and
the individual aberrations are satisfactorily corrected.

[0090]As tabulated in Table 5, moreover, the conditional expressions (1),
(1'), (2) and (3) are satisfied according to the projecting zoom lens of
Embodiment 4.

Embodiment 5

[0091]The schematic constitution of the projecting zoom lens according to
Embodiment 5 is shown in FIG. 5. The projecting zoom lens according to
Embodiment 5 is given a constitution substantially similar to that of
Embodiment 1 such that the fifth lens group GS also has a negative
refractive power, but is different mainly in that the first lens group G1
includes the first lens L1 made of a negative meniscus lens having a
convex face directed to the magnification side and the second lens L2
made of a biconcave aspheric lens in the paraxial region, and in that the
fourth lens group G4 consists of the fifth lens L5 made of a positive
lens.

[0092]Here, the projecting zoom lens of Embodiment 5 is different in the
lens number from Embodiment 1, so that the given lens numbers are
sequentially shifted according to the differences.

[0093]In this Embodiment 5, the radius of curvature R of each lens face,
the center thickness of the respective lenses and the air distance D
between the respective lenses, and the refractive indices Nd and the Abbe
numbers vd at the d-line of the individual lenses are tabulated in Table
5.

[0094]Moreover, the third surface (or the surface of the magnification
side of the second lens L2) and the fourth surface (or the surface of the
reduction side of the second lens L2) are made a spheric, and the
respective values K, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14,
A15 and A16 are tabulated for those individual aspheric surfaces in the
lower column of Table 5.

[0097]According to the projecting zoom lens of Embodiment 5, as apparent
from FIG. 11, the angle of view 2ω is as wide as 57.4 degrees, and
the respective aberrations are satisfactorily corrected.

[0098]As tabulated in Table 5, moreover, the conditional expressions (1),
(1'), (2) and (3) are satisfied according to the projecting zoom lens of
Embodiment 5.

Embodiment 6

[0099]The schematic constitution of the projecting zoom lens according to
Embodiment 6 is shown in FIG. 6. The projecting zoom lens according to
Embodiment 6 is given a constitution substantially similar to that of
Embodiment 1, but is different mainly in that the first lens group G1
includes the first lens L1 made of a negative meniscus lens having a
convex face directed to the magnification side and the second lens L2
made of a biconcave aspheric lens in the paraxial region, in that the
positive lens L4 included in the third lens group G3 is made of a
positive meniscus lens having a convex surface directed to the
magnification side, and in that the fifth lens group G5 is constituted to
have a positive refractive power.

[0100]Here, the projecting zoom lens of Embodiment 6 is different in the
number of lenses from Embodiment 1, so that the given lens numbers are
sequentially shifted according to the differences.

[0101]In this Embodiment 6, the radius of curvature R of each lens face,
the center thickness of the respective lenses and the air distance D
between the respective lenses, and the refractive indices Nd and the Abbe
numbers d at the d-line of the individual lenses are tabulated in Table
6.

[0102]Moreover, the third surface (or the surface of the magnification
side of the second lens L2) and the fourth surface (or the surface of the
reduction side of the second Lens L2) are made a spheric, and the
respective values K, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14,
A15 and A16 are tabulated for those respective aspheric surfaces in the
lower column of Table 5.

[0107]where fw denotes the focal length of the whole lens system at the
wide angle end, f1 denotes the focal length of the first lens group,
νd4 denotes the Abbe number of glass material forming the positive
lens contained in the fourth lens group G4 and Nav denotes mean value of
the refractive indices at the d-line of the glass material of which the
positive lens in the second lens group and the glass material of which
the positive lens in the third lens groups.